This invention relates to a sealed type casing used for base station equipment for portable telephones and, more particularly to a miniaturized sealed type casing adapted to efficiently radiate the heat generated in the interior thereof.
With the recent advancement of techniques, the miniaturization of a sealed type casing used for base station equipment for portable telephones is progressing year by year. As the miniaturization of the sealed type casing progresses, the quantity of heat generated therein per unit volume of the casing increases, so that a radiating structure more efficient than a conventional structure of this kind is demanded. Simultaneously with the progress of miniaturization of the sealed type casing, the number of the casing installed outdoors increases. Accordingly, the necessity of such a sealed type casing to meet the waterproofing conditions as well is increasing.
A conventional sealed type casing for communication machines and tools is shown in FIGS. 1 and 2. A sealed type casing 20 for communication machines and tools comprises a casing body 21 and a cover 25, and the casing body 21 is fixed to an electric pole by two straps 3. A radiator (heat radiator) 22 made of aluminum is fixed to the casing body 21 by screws 24 via waterproof packings 23, and adapted to radiate the heat occurring in a heating unit 17 provided in the interior of the casing body 21 to the outside thereof. A cable 4 of a power source wire and a communication wire is drawn from a bottom portion of the casing body 21 thereinto.
However, the radiation of heat from the interior to the exterior of the sealed type casing 20 for communication machines and tools is carried out in the form of natural radiation of heat from the casing body 21 and radiator 22, so that a surface area of the casing body 21 is necessarily increased. This necessarily causes the dimensions and weight as well of the casing body 21 to increase. Since the radiation characteristics of the radiator 22 are influenced by an external wind velocity, a radiating effect of the radiator 22 decreases in a windless condition. Since the air is made to flow in a plurality of grooves in the radiator 22 by utilizing a convection current, it is necessary that each groove of the radiator 22 faces in the vertical direction so as to permit the heated air to be discharged from the grooves. This causes inconvenience since the direction in which the sealed type casing 20 for communication machines and tools is fixed to the electric pole 2 is restricted.
Another conventional cooling apparatus for electronic machines and tools is shown in FIG. 3. This cooling apparatus for electronic machines and tools is disclosed in Japanese Unexamined Patent Publication (JP-A) No. 32300/1992. A box type casing 31 for housing various kinds of electronic parts therein is divided into two chambers 33, 34 by a heat insulating partition 32. A first chamber 33 houses therein a control electronic part 41, such as a printed circuit board of a low thermal resistance, and a second chamber 34 houses therein an electronic part 42, which has a large quantity of generated heat, for a main circuit. Therefore, a fan 43 for agitating the air in the interior of the second chamber 34 is provided therein, and a cooling member 44, such as a radiating fin is also provided on an outer surface of the electronic part 42 for a main circuit.
However, in this cooling apparatus for electronic machines and tools, the control electronic part 41 generally has a low thermal resistance, so that it is necessary to increase a surface area of the box type casing 31 for increasing the cooling effect. The greater part of the generated heat in the interior of the box type casing 31 is caused by the electronic part 42 for a main circuit. The greater part of the generated heat in the electronic part 42 for a main circuit is radiated from the cooling member 44 but a part thereof is radiated with the generated heat of the control electronic part 41 from an outer surface of the box type casing 31. The control electronic part 41 is influenced by the generated heat of the electronic part 42 for a main circuit. Since the fan 43 and cooling member 44, such as a radiating fin are used in the cooling apparatus for electronic machines and tools, the miniaturization of the apparatus as a whole and the simplification of the construction thereof have not yet been attained.